SAR 940 Racing Engine - Beyond All Measure

When it comes to making horsepower, the thought that bigger is better has driven the motorsports hobby for years. In the late 1950s, the first 348 ci big-block Chevrolet spawned an infamous family of engines ranging from the 409 in 1961, and then the 427 Mystery Motor two years later. With a 4.840-inch bore center and 9.800- to 10.200-inch deck height, the next generation of big-blocks opened the door for engines with displacements of 396, 454, 472 and 572 ci, which is at the top of the food chain for GM big-block crate engines.

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Even so, the demand for greater horsepower continued to grow as stock Rat motors gave way to strokers, which in turn, stepped aside for a rash of mountain motors.

Starting at around 632 ci, cubic inch inflation began to push the limits of conventional thinking. Engine builders responded with aftermarket blocks with spread pan rails, revised cam locations and raised deck heights, but they began to hit a brick wall when it came to getting much more than 700 ci out of an engine block. Sonny's Automotive Racing (SAR) helped break that barrier years ago by developing stretched engine blocks with 4.900-, 5.000- and then 5.300-inch bore centers.

By stretching the block to provide a bigger combustion chamber, larger bore and broader power band while still maintaining optimal valvetrain geometry, a larger engine with a higher base power level would provide builders much more flexibility, no matter what kind of power adders they used. Spraying less nitrous would lead to blowing less gas past the exhaust valve, smaller turbos would give quicker spool up and smaller blowers would lead to less engine wear. With the greater range of choices that a bigger engine provides, crew chiefs in Pro Mod, Outlaw 10.5 and Top Sportsman suddenly had more options and flexibility in putting an engine combination together.

Today, the evolution of this engine species continues to evolve as SAR has released a new 940 ci monster motor that represents the top of the food chain in naturally aspirated engine technology (and price). Representing the top of the mountain in the 5.300 engine family, this new 940 engine, even in this pump gas configuration, provides a number of advantages over the smaller, but better known IHRA Pro Stock engines that have produced the quickest and fastest N/A quarter-mile doorslammers in the world.

"No matter whether it's F1, NASCAR or drag racing, the trend over the past few years have been to go with a larger bore and less stroke in order to move the power band up," said Sonny Leonard. "An 825 ci engine will typically use a 4.800-inch bore with a 5.700 stroke. Here, we're using what cleans up to a 5.080 bore with a 5.800 stroke. As a result, the engine is much easier on the rods, makes more power and actually costs less, too."

Of course, brute power is what any of the 5.300 family of monster motors is all about. Dyno tests on this particular engine showed a whopping 1,702 peak horsepower at 7,200 rpm with 1,357 lb-ft of torque at 6,000 rpm on 93 octane pump gas. By comparison, this is nearly 2.5 times the peak power of a 720hp ZZ572/720R crate engine. Figure to spend just under a hundred grand for the 940 in this article.

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SAR 940 Racing Engine - Beyond All Measure

To build an engine this large, SAR started with a 5.300-inch bore center block, which is seen here compared to the standard 4.480 bore center Chevy big-block. Introduced in 2007 with a wider bore center, raised cam location and spread oil pan rails, SAR has used this as the basis to build some of the largest engines in the aftermarket with both hemispherical- and wedge-style cylinder heads.

Unlike solid blocks found in most high-end race applications, SAR used special proprietary water passages around each cylinder for cooling on this pump gas engine to help control potential engine destroying detonation. CNC machine aluminum end plates are removable for access to these areas which are usually inaccessible.

Compared to the stock crankshaft on the left, the billet steel Sonny Bryant crank used in this 940 ci engine on the right looks considerably bigger. To accommodate the massive 5.800-inch stroke, SAR's block was designed with a raised cam location and widened oil pan rails. Additional milling was done to provide clearance for the massive counter weights.

Since the low octane of a pump gas engine makes it more prone to detonation, selecting the right connecting rod is pretty important. SAR used Carrillo steel rods (bottom) measuring 7.995 inches in length center-to-center as opposed to the stock style rod (above) which measures 6.135 inches. The big bore end retains its stock configuration of 2.325 inches while the pin bore was increased from 0.990- to 1.031-inches.

While the hubcap-sized item on the left could pass for something else, it's actually the 5.080-inch diameter dished piston that's used in this insane engine combination. SAR can use anything from a 5.000-inch to a 5.100-inch bore with different stroke combinations in this series of engines with the 5.300 bore center blocks. In comparison, the bore on a standard 454 big-blocks measures 4.251 inches.

When compared to a stock BBC cylinder head (left), it's easy to see how much different the combustion chambers look on SAR's semi-hemispherical cylinder heads features with their revised valve and spark plug locations. These heads can flow up to 670 cfm on the intake and 430 cfm on the exhaust side runners. SAR also offers a wedge-style ahead for their 5.300 block, which flows 660 cfm on the intake and 450 cfm on the exhaust sides.

With the flow that these heads have, getting air into and out of the combustion chamber at high rpm requires big valves. SAR uses valves ranging in size from 2.650 to 2.850 inches on the intake side and 1.900- to 2.100-inch on the exhaust on the semi-hemispherical head and intake/exhaust valves ranging up to 2.760/2.000-inch on their wedge head design for this particular engine family.

With the valve cover off, it's easy to see how SAR's semi-hemispherical head has a much more complicated valvetrain than what's typically seen on a wedge- style head. The advantages of a more direct airflow, larger valves and superior combustion chamber design more than makes up for the complexity, larger size and additional weight.

Shooting fuel from the billet fuel rail down directly towards the intake valve are massive 160 lb/hr low impedance fuel injectors, which are actuated by a programmable Big Stuff 3 engine management system with an advanced 16-bit microprocessor.

While this engine made over 1,700 hp without nitrous on pump gas, the customer of this particular engine ordered it with nitrous. On the back side of each hand-formed intake runner is a moderate three-stage fogger nitrous system which can deliver another 800 hp on demand. Routing the lines and nozzles under the top of the sheet metal intake provides a much cleaner looking installation.

To minimize the chance of damage in case of a nitrous accident, the back side of the manifold plenum comes with a nitrous burst panel with 7-pound springs, which is designed to reset itself should it ever pop off.

Accufab crafted these billet aluminum throttle bodies with massive 2.500-inch bores just for EFI monster motors like this. Accufab throttle blades were used along with Sonny's progressive linkage to bring this monster motor to life as the throttle is depressed.

With over 40 years of building some of the biggest and baddest Chevy engines on the planet, SAR's Sonny Leonard has a long list of technical achievements, world records and series championships associated with his name.

SAR used a MSD flying magnet crank trigger to stabilize the ignition timing on this 940 ci pump gas engine. This arrangement utilizes four magnets in the aluminum trigger wheel which trigger the ignition when they pass by the stationary non-magnetic pickup seen on the lower left. This "flying magnet" design produces accurate trigger signals and the non-magnetic pickup cannot be false triggered.

Priced in the high eighties, nearly 250 hours of labor went into this engine, which covered everything from milling the block to the final adjustments on the throttle linkage. Nearly every part was custom made or designed just for Sonny's Automotive Racing.

Low profile, chrome plated valve covers that were buffed to a mirror finish were fabricated by Moroso especially for this pump gas monster motor.